Fluid transmission



June 11, 14935.

E. J. svENsoN FLUID TRANSMISSION Filed Dec. 26, 1930v 2 Sheets-Sheet l A @YY/ Z079 l 2377722 .si J 52/@77/50/2 June 11, 1935. E. .1. svENson FLUID TRANSMISSION Fil'ed Dec. 26,` 19:50

2 Sheets-Sheet 2 Raf/2712507? l lfrvzesi 5u@ uson @MQW W QW/5 -employ a pump,

any possible Patented AJune 11, 1935 STATES PATENT oF-Ficl-z amaca FLUID TRANSMISSION Ernest J. ,Svensom Rockford, lll. Application December 26, 1930, Serial No. 504,810

l2 Claims.

My inventionv relatesv generally to material working apparatus, and more particularly to hydraulic systems of control therefor. It is one of the objects of my present invention to provide a hydraulic system of control, in which an improved practical closed circuit serves to control the shifting of a machine element, such as a work supporting carriage or the like.

More specifically, it is an object of my invention to provide an improved closed hydraulic circuit as set forth above, which is particularly adaptable for use in connection with the reciprocation of a machine element, as, for example, the reciprocation of a table in av metal working machine, such as a grinding machine.

My invention also contemplates a new and improved adaptation for high displacement pumping devices, such as gear pumps and the like, by using sai-d pumps ina circuit as set forth above for eecting the movement of a shiftable or reciprocable machine element.

Another object of my present invention is to such as a gear pump, in a circuit so that said pump will operate as a lock to prevent the shifting of the propelling fluid body in a closed circuit under certain conditions, and under other conditions to eiiectthe Ilow of uid in said circuit.

A still further object of my invention is to provide, in combination with a relatively-large displacement pumping mechanism and conduits connecting same with a machine element, a simple and effective control valve mechanism.

VIn addition'to the above mentionedadvantageous structural features, my invention contemplates the provision of a new and improved means for taking care of any losses due to leakage in the low pressure side of the circuit resulting from wear in the reciprocating parts, and to this end I propose to employ a continuously operating pump, such as a gear pump. y

Still another object of my invention is to provide, in combination with a shiftable machine element' or the like, an improved hydraulic actuator system which includesa pump, such as a gear pump, for imparting rapid traverse to the machine element, and a second pump of smallerV displacement which is adapted to take care of r leakage resulting from wear inthe reciprocating parts, but which is suiilciently impositive in action to permit the return of uid therethrough to a suitable reservoir without aifec'ting the functioning of the mainpump. l

The foregoing and numerous other objects and advantages will be more apparent from the fol- ,being shown in section lowing detailed description when considered in connection with the accompanying drawings, whereinl l v Figure l is a fragmentary elevational view of a material working apparatus or and certain of the fragmentary hydraulic control elements associated therewith, said machine being representative of one type which `may be hydraulically controlled in a very efficient manner by practicing the teachings of my present invention;

Figure 2 is an enlarged central sectional view of the main propelling pump for imparting rapid traverse to the machine carriage;

Figure 3 isa fragmentary enlarged sectional view of the pump employed to continuously maintain a predetermined pressure in the low pressure side of the main control circuit; and

Figure 4 is a semi-diagrammatic representation of my improved hydraulic actuator system, the reversing and starting and stopping valves in order to more clearly understand the functioning thereof.

designate similar parts throughout figures, it will be observed that for the purpose of illustrating one practical embodiment of the invention, and not in any sense by way of limitation, I have disclosed fragmentarily certain portions of a material working apparatus vor grinding machine, which I have designated generally by the numeral IILFigure l. This grinding machine includes a suitable base I2 and a work supporting carriage I4, which .is reciprocable upon the upper portion of said base. EX- tendingV upwardly from the base I2 is a frame I6 which supports a suitable rcutting element or grinder wheel I8. Rotation may be imparted to the grinderwheel I8 by any suitable means, such as an electric motor or the like (not shown), and reciprocation to the work supporting carriage I4 is occasioned by means of a hydraulic actuator system, about to be described. 45

This hydraulic actuator system of control includes a cylinder 20, Figure 4, which maycbe housed within thebase I2 and beneath the reciprocable carriage or machine element Il. Pistons 22 and 24 are reciprocable within vtheir respective cylinder chambers 22a and 24a, and con- -nect at their outer extremities with brackets 26 depending from and secured to the opposite extremities of the carriage I4.

In a grinding machine of the type shown the work piece l(not shown) is mounted in anysuitgrinding machine 5 nage is then shifted so cates with radial able manner upon the caniage I4, and said caras to reciprocate the supportedwork piece beneath the cutting tool or grinder I 8. In order to effect the reciprocation of the pistons 22 and 24 and thereby control the reciprocation of the carriage I4, I employ a suitable main pump, which I have designated generally by the numeral 28. In the disclosed embodiment, this pump 28 is similar to the pump disclosed in my copending application, Serial No.

430,868, led February 24, 1930, now Patent Numf ber 1,912,737 which is of the variable displacement type. This pump 28 includes a suitable housing38 and a pair of meshing gears 32 and 34 15 suitably mounted within Vsaid housing. The gear 32 is mounted upon and 'driven by a drive shaft 36, and the gear 34 is mounted upon a. valvemember 38 which is provided with a peripheral port 40.

Fluidi is introduced or delivered to an intakeA chamber 42 of the pump 28 from a pipe line 44,

and when the gears 32 and-34 rotate in the direction indicated by the arrows, Figure 2, the introduced fluid is carried along the periphery of the gears and compressed within the discharge chamber 46 which connects with a suitable pipe line 48. The gear 34 is provided with radial ports 50 and 52 which serve to receive fluid trapped between the meshing gear teeth, and these ports communicate with the valve port 40, as clearly shown in Figure 2. 'I'he valve 38 may be adjusted by manipulating a suitable control handle 54, Figure 4, so as to adjust the position of the valve port 46. In this manner I am able to adjustably control or regulate the displacement of the pump 28. Thus, if the valve 38 is shifted in a counterclockwise direction, I am able to effect the delivery of a certain portion of the iluid from the high pressure-or discharge chamber 46 to the low pressureor intake chamber 42, and in this manner regulate the displacement of the pump. For

a more detailed explanation of the functional characteristics of this pump reference is again made to my above mentioned patent.

Fluid under pressure, which is received by the pipe line 48, is delivered to an intake port 56 of a suitable reversing valve, which I have designated generally by the numeral 58. This valvel includes a central valve casing 68 and end casing sections 62 and 64, which are secured in any suitable manner 4to the central section 6II. Reciprocable within these valve caslngs is a valve meman intermediate cylindri- 68 and 'I0 formed integral therewith. When the valve 66 occupies-the position shown in Figure 4, fluid from the .pipe 48 is directed through the port 56, which is in continuous communication with a central annular valve port 1 2. Fluid from this annular port 'I2 passes through Aradial ports 'I4 and then into a central longitudinal passage 16. The left extremity of this passage 'I6 communicates with radial ports 18, which at this linstant are closed by the valvecasing 80. The

opposite extremity-of the passage 'I6 communiports 88, which at this instant register with an annular port 82. A pipe line 84 is connected with this annular. port 82, and thus fluid is directed by saidvalve from the pump 28 into the pipe line 84, which is connected with the right end of the cylinder chamber 22a. Thus, by directing'fluid into thecylinder chamber 22a, the carriage I4 is urged to the left, Figure 4.

Fluid from the cylinder chamber 24a is ejected through the action of the piston 24 and is directed the pipe line -justably mounted upon said carriage is moved into engagement with the right end of the reduced cylindrical section 'I0 of the valve member 66, as clearly shown in Figure l, thereby causing said valve member to be shifted to the left. In this shifted position the direction of fluid flow within the pipe lines 84 and 86 is reversed, thereby causing the carriage to be shifted to the right. Fluid returned by the pipe line 84 is noW directed by the annular port 82 to a valve chamber 96', which communicates with the return pipe 44 through the two-branch passage'92. When the carriage I4 reaches the limit of its movement to the right, Figure l, a dog 98 adjustably mounted upon said carriage engages the left end of the valve member and thereby effects the automatic reversalv of the carriage.

Attention is directed to the fact that as the valve 66 in Figure 4, communication between the valve chamber and the conduit or pipe line 86 is restricted and likewise communication between the pipe line 84 and the radial port 80 is restricted. Thus, the propelling effectiveness of the uid in 84 is decreased, and this results in a slowing down of the table I4.' In view of the fact that the valve 66 is subjected to balanced uid conditions atv either end thereof, very slight power is required to shift it. Thus,- the momentum of the carriage I4 is suiiicient to carry the valve to its extreme left position. It should also be notedfthat the annular ports 82 and 88 are never completely cut off; that is to say, the width of these ports is greater than the thickness of the metal at each end of the valve 66l adjacent the radial ports 'I8 and '88. `Therefore, when the valve 66 approaches its central positionv in its movement to the left, fluid pressure developed by the gear pump 28 will have a breaking effect upon the actuator piston 24, but'the momentum of the carriage I4 will be suiicientto shift the valve to its extreme left position..

From the foregoing it will be apparent that my invention contemplates the provision vof a closed hydraulic circuit for effecting reciprocation' of a machine element, such as the carriage I4, and this closed circuit includes the gear pump 28, the hydraulic actuator including the pistons 22 and 24', reversing valve 58. By driving the pump 28 at a predetermined desired speed .and having the valve 38 properly adjusted, a definite uniform displacement of uid to the intake side of the cylinder 20 is obtained, and the same uniform displaceshifts'to the left from its position shown the connecting pipe lines, and the ment of fluid from the discharge side of the ,fluid leaks from one side of the pump to the other through the meshing teeth of the gears, and hence it may be stated that' the pump 28 displaces at a uniform rate a predetermined body of fluid to effect the movement of the carriage in a given direction, and receives the same predetermined volume of fluid from the discharge side of the carriage actuator. The fluid cannot be discharged from the pump any faster than it is bers 22a and 24a suicient `ber |06 upwardly,

' ,suitable drive shaft 36a andthe gear 34a received, nor can it be received any/faster than .t is discharged. Therefore, if no leakage takes place in the actuator, a predetermined volume of iluid is maintained in the circuit, and the entire body of fluid in the 4circuit ,is subjected to a reversal of flowupon each ^actuation of the reversing valve. n

lIn order to render the constantly driven gear pump 28 functionally inoperative, it is only necessary to swing a control handle conveniently positioned at the front of the machine, as shown in Figure l, to the right. This handle |00 is mounted upon a shaft |02, which carries an arm |04, Figure 4, and the outer end of this arm makes a slotted connection with the lower extremity of a valve member |06, and this valve member forms a part of a mechanism, which I have termed a starting and stopping valve, denoted generally by the numeral |08. When the valve |06 is shifted upwardly, the closed circuit just described is short circuited, and fluid is free to flow from one side to the other. Thus, for example, if the reversing valve is positioned as shown in Figure 4, andthe starting and stopping valve |08 is actuated so as to shift the valve memcommunication is .established between the pipe line 84 and the pipev line. 86 through a pipe or conduit I0, a valve port ||2, an annular valve port |4, a valve 'port H6, and a pipe or conduit ||8. By permitting this short circuiting to take place, the fluidwill follow the 'path of least resistance, and hence will circulate between the pipe lines 84 and 86 without developing a pressure within the cylinder chamto effect the shifting of the carriage I4. As soon as the control handle ||0 is again shifted to the left and the valve member |06 is lowered, communication between the pipe lines 84 and 86 is'closed and the pump 28 again rendered functionally operative to eiect reciprocation of the machine carriage.

Attention is now directed to a pump |20, which is similar in structural characteristics to the gear pump 28. TheV displacement of the pump is considerably less than the displacement of the main pump 28. This gear pump |20 includes a casing 30a corresponding to the casing., 30 of the pump 28 and a pair of gears 32a and 34a, the gear 32a being muntedupon and driv n'by a ing rotatably mounted upon an adjustable valve 38a, which valve is provided with a peripheral port 40a. Fluid is directed to an intake chamber 42a of the pump |20 from a suitable reservoir |22 through a pipe or conduit |24. Fluid from the intake chamber 42a is carried along the periphery of the gears and subjected to increased pressure within a discharge chamber 46a, and from this chamber the uid may be directed through a pipe line |26 which connects with the pipe line 44. It should be noted that the valve 38a of the pump |20 is `so positioned that the,port 40al thereof will permit fluid from the discharge chamber 46a to be conducted through radial passages or ports 50a and 52ato the intake'chamber 42a. By em/ plo;J ing this construction, the pump |20 is Crendered impositive in action; that is to say, said pump is driven so as to setup a predetermined necessary pressure within the pipe line |26 to take care of any possible leakage in thecarriage actuator, and if additional uid'to take care of leakage is not required, the valve port 40a permits the continuous circulation of uid 'from the high pressure to the low pressure side of the pump |20. The size of the ports within the pump |20 lvision of a new and is suiilcientlyi'restricted so that. the operating pressures within the'y closed circuit described above is continuously maintained. The pumps 28 and |20 may be continuously driven from a common source of power supply, for example, electric motor |28 shown Figure 4, and which may be mounted within the machine structure in a conventional manner. As stated above, the displacement of the pump |20 need be very small in comparison with the displacement of the pump" clearly disclose thestructural features loi? these pumps, I have .shown vthe same 'in Figures 2 and 3 as being of substantially the same size. However, variations in the relative sizes of the pumps erating circuit.

From lthe foregoing parent that my invention contemplates the proimproved closed circuit, which is capable of employing a high displacement pump therein, such'as a gear pump. The arrangement of the operating circuit described above is such that the main gear pump serves to lock the fluid body on each side of the circuit; that is to say, the side of the circuit functions entirelyindependa' suitable ldiagrammatically in y description it' will be *apa l 28. In order tomore will depend entirely upon thev pressures, v etc., whichL are to be maintained within the opfluid body 'in the low pressure H l ent of the uid body in the high pressure side iof the circuit, and vice-versa. Byemploying my invention, a relatively high displacement pump, such'as a gear pump, employed to impart rapid traverse to machine elementss Reciprocating rapid traverse movements of machine elements is tical in machines, such as grinding machines, where'it is desirable to effect relative reciprocation betweenthe cutting tool or grinder and the 'Work piece. My invention has a very practical application in such instances. 'I'he simple arrangement of the control valves,

valve, enables my system ofl hydraulicAcontrol to be veryeconomically produced.'

'I'he gear pump |20 for taking care of any leakage in the operating circuit, presents a very particularly pracincluding the. reversing valve and the starting and stopping .may be very effectively practicalarrangement, and is superior in func- Ational characteristics' to other mechanical devices, such as spring devices, which have been employed heretofore in'fsome Either the pump 28 or the pump |20 maybe adjusted to vary the displacement thereof by a simple shifting of externally positioned hand lever, and these pumps are of extremely simple .and practical design. They -are so arranged as to relieve against the `and slippage between the gear teeth, andas such eliminate the development of heat within the huid body. The gear pumps may be driven from a common source oi' power supply, and in instances where it is desirable, said pumps, -as well as the grinding wheel I8, may be driven from a common driving mechanism, such-as" an electric motor.

My improved system of control is particularlyA fluid circuits.

development of pressures f well adapted for use with grinding machines,

the-movement of the carriage mentfa wavy surface instead of an absolutelyv -as being reciprocable in given directions, but

obviously the carriage may be moved in directions which vary from that disclosed in the drawings, by employing the teachings of my invention.

While I have disclosed a particular metal working apparatus or grinder for the purpose o! illustrating one practical application of my in-Y vention, it should be clearly understood that said invention is by no means'limited tosuch a machine structure, noris the invention limited to the other specific structural features disclosed in the drawings, but is capable of other modiiications and changes without departing from the spirit and scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In wmaterial working apparatus, a work support, a cutting Itool, said work support and cutting tool being relatively movable, a hydraulic actuator for effecting relative movement between the work support and the cutting tool, a

constant speed variable displacement gear pump connected in a closed circuit with said actuator, the pressure maintained at the gear pump exhaust being substantially the same as the pressure oi the uid which propels the actuator, `pump means for maintainingl pressure at the intake side of the gear pump, the pressure thus maintained counteracting the suction effect at the gear pump intake, a reservoir for supplying uid to said pump means, and a valve mechanism for controlling the reversal of said actuator, said valve being operable in response, to the shifting of said actuator. C

2. In material working apparatus, a work support, a cutting tool, said work support and cutting tool being relatively' movable, a hydraulic' actuator for effecting relative movement between Y the work support and the cutting tool, a constant speed variable displacement gear pump connected in a closed circuit free from relief valves with said actuator whereby a pressure is maintained at the gear pump exhaust which is substantially the same as the pressureoi the iluid serving to propel Ythe actuator, a reservoir, and pump meansinterposed, between the gear pump and said reservoir for maintaining communication' between said gear pumpand reservoir and for maintaining pressure at the intake ofthe gear pump to counteract suction eil'ects.

- l3'. In a lhydraulic 'actuator system, ,1a-reciprocable hydraulic actuator, a gear pump, means connecting said gear pump directly with said' actuator without the use of relief valves, whereby the volume of uid displaced by the gear pump to the intake side ot the actuator is substantially equal to the volume of iluid received by the gear pump from the discharge side oi' said actuator andwhereby a pressure is maintained at the gear pump exhaust which is substantially the same as the pressure of the iluid serving to propel the actuator, and a second pump 191'. maintaining pressure at the intake side of the'y gearl pump to counteract suction effects at the gear pump intake and for maintaining communication between said gear pumps and the intake side of said second pump.

4. In a hydraulic actuator system, a reciprocable hydrauliclactuator, a gear pump for imparting movement to said actuator, means connecting said gear pump with said actuator, and aV variable displacement gear pump oi' lower displacement than the rst'mentioned 'pumpl for supplying iluid to maintain a uid body under pressure between the actuator and the intake of said rst mentioned gear pump and thereby take care of any leakagein `said actuator and also to counteract suction effects at the intake of said iirst mentioned gear pump.

5. In material working apparatus, a work support, a cutting tool, said work support and cutting tool being relatively the work-'support and the cutting tool, a 'gear pump connected in a closed circuit with said actuator by ducts free from relief valves wherebyarrest the movement of said actuator, a reservoir,

and pump means for receiving fluid from said reservoir and impositively urging said iiuid toward the intake of said gear pump.

6. In material working apparatus of the class described, a grinder, a work supporting carriage for reciprocating a work piece past said grinder, a hydraulic actuator for reciprocating said carriage, a variable displacement gear pump connected in a closed circuit with said actuator, and a valve mechanism for controlling the reversal of said actuator, said valve mechanism including a normally balanced valve member shiftable solely in response to the movement of said carriage.

'7. In a hydraulicactuator system, a hydraulic actuator including a piston within al cylinder, a variable displacement gear pump for propelling said actuator, andfa second variable displacement gearA pump connected with the intake side L of they rst mentioned pump for maintaining a gear pump, and means for adjusting the displace?` gear pumps independently'of l ment offone of the the other.

Y9. Ina hydraulic actuator system, a hydraulic actuator including a cylinder and a piston therein, agear pump-for propelling said actuator, a shiftable valve for controlling the direction of flow of iiuid from saldgear pump to said actuator, and a second pump connected with the intake side of said gear pump and adapted through the agency of said valve to communicate with the return side of\` said actuator, whereby to maintain uid pressure \,within the return side of said actuator and J the intake side or said gear pump to counteract suction eii'ects at the gear pump intake.

10. In a hydraulic actuator system, a hydraulic actuator including a piston and cylinder construction, a gear pump, a duct free from relief valves connecting the discharge side of said pump with one side of said actuator, a duct free from relief valves connecting the intake side of said pump with the other side of said actuator wheremovable, a hydraulic 1 `actuator for eilecting relative movement between by to connect said actuator and pump ina closed circuit, the gears of said pump having means for relieving against uid pressure developed at the meshing zone of the gear teeth and for preventing the slippage of uid from the high to the low pressure side of the pump through said meshing teeth whereby to enhance the operative effective-4 ness of said closed circuit, and means for controlling the operative functioning of said pump with respect to said actuator.

11. In a hydraulic actuator system, a. hydraulic actuator for propelling machine tools and the like; a pump, a duct free from relief valves extending 'between the discharge of said pump and the intake of said actuator, a similar duct connecting the opposite sides of said actuator and pump, a iiuid reservoir, means interposed between said reservoir and the intake of said pump including -a second pump for maintaining fluid "pressure at the intake side of the first pump and means for continually maintainingpommunication between the reservoir and thglintake side of the rst pump without affecting the operative functioning of the second pump to maintainpressure, whereby to effectively counteract suction eiects produced at the intake side of the rst pump and vthereby preclude the entrance of air within the system, 4and valve means for controlling the direction of uid delivery to said actuator.

12. In combination with a shiftablemachine element, a hydraulic actuator for shifting said element. a source of uid supply, a pump for 'receiving fluid from said source and delivering ythe fluid to said actuator, a valve mechanism thereby cause said valve member to be shifted from one to another of said positions, said means providing the sole propelling medium for said valve member.

ERNEST J. SVENSON. 

